NICKEL AND ITS ALLOYS
Nickel is largely used for nickel plating and for coins of low value, and
also occurs in many alloys.
Descriptions will be given here of the tests to be made on commercial
nickel and of the analysis of german silver and the like, which are the most
important nickel alloys. For the analysis of bronzes containing nickel, see
The more common determinations involved in the analysis of com-
mercial nickel are those of copper, cobalt, iron, manganese, carbon, sulphur,
arsenic and silicon.
10 grams of the sample are dissolved in nitric acid and evaporated in
presence of sulphuric acid until dense white fumes appear. When cold
the residue is treated with water acidified with sulphuric acid, heated to
boiling, filtered and washed with boiling water acidified with sulphuric
acid. The residue on the filter is treated according to I and the filtrate
as described in 2, 3 and 4.
1. Determination of the Silicon.—The insoluble residue, consisting
of silica and possibly metastannic acid, graphitic carbon, etc., is dried,
ignited in a platinum crucible, weighed, treated with hydrofluoric acid
and a few drops of sulphuric acid, heated to expel excess of acid, again
ignited, cooled and weighed. The loss in weight gives the silica and there-
fore the silicon (see Determination of the Silicon in Iron).
2. Determination of the Copper.—The copper is precipitated in the
filtrate by means of hydrogen sulphide and is then determined either as
oxide or electrolytically by dissolving the sulphide in nitric acid and elec-
trolysing the solution.
3. Determination of the Nickel and Cobalt.—(a) Determination
of the nickel. The filtrate from the copper sulphide is made up to volume
in a 500 c.c. measuring flask, and 100 c.c. (corresponding with 2 grams of
the sample) evaporated to dryness. The residue is taken up in ammonia
and the volume then made up to 100 c.c. with ammonia (D 0-91), 5 grams
of ammonium sulphate being dissolved in the liquid and the latter elec-
trolysed to determine the nickel and cobalt together : Winkler cathode J
spiral Winkler anode J ND100 = 0-7-1 amp.; temperature, ordinary, and
duration, 15-17 hours.
The cathode is subsequently withdrawn, washed, dried and weighed,
the increase in weight representing nickel and cobalt J the latter is then
determined separately as follows:
(b) Determination of the cobalt.1—The nickel and cobalt deposited on
the electrode are dissolved in nitric acid, the solution evaporated to dryness,
the residue taken up in a little water and evaporated with 20 grams of pure
ammonium thiocyanate until the salts begin to crystallise out, and the
whole washed by means of a little water into a Rothe extraction apparatus.
1 Ber. deutscJi, Chem. Gesell., 1901, XXXIV, p. 2050. very small amount, it is more convenient to make